Shallow-water late middle Eocene crinoids from Tierra del Fuego: a new southern record of a retrograde community structure
One of the very few crinoid records in Patagonia is that of the abundant columnals of the genus Isselicrinus found in several localities in shallow marine, glauconitic sandstones of the Leticia Formation (upper middle Eocene of Tierra del Fuego Island). Some of them, up to 10 cm long, are preserved...
| Published in: | Scientia Marina |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Consejo Superior de Investigaciones Científicas
2005
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| Subjects: | |
| Online Access: | https://scientiamarina.revistas.csic.es/index.php/scientiamarina/article/view/339 https://doi.org/10.3989/scimar.2005.69s2349 |
| Summary: | One of the very few crinoid records in Patagonia is that of the abundant columnals of the genus Isselicrinus found in several localities in shallow marine, glauconitic sandstones of the Leticia Formation (upper middle Eocene of Tierra del Fuego Island). Some of them, up to 10 cm long, are preserved in a position almost perpendicular to the stratification, which is attributed to episodes of high sedimentation rate. The Isselicrinus remains occur either almost alone or associated with solitary corals, gastropods, bivalves, rare nautilids, shark teeth, penguin bones and well-preserved specimens of Ophiura elegantoides. The associated microfossils, mainly Foraminifera, are characterised by the anomalous abundance and dominance of large Nodosariacea. These records reflect a peculiar success of a retrograde, dense, suspension-feeding crinoid population as a regional extension of previously described distribution in the Antarctic upper Eocene. Uno de los pocos registros de crinoideos en Patagonia está representado por abundantes columnas del género Isselicrinus, en areniscas glauconíticas someras de la Formación Leticia (Eoceno Medio superior de Tierra del Fuego). Algunas columnas, de hasta 10 cm de largo, están preservadas en forma casi perpendicular a la estratificación, posición que se atribuye a episodios de alta tasa de sedimentación. Los restos de Isselicrinus se presentan en forma aislada o están asociados a corales solitarios, gastrópodos, bivalvos, escasos nautiloideos, dientes de tiburones, huesos de pingüinos, y ejemplares bien preservados de Ophiura elegantoides. Los microfósiles asociados, principalmente foraminíferos, se caracterizan por la dominancia y abundancia anómala de grandes conchillas de Nodosariacea. Estos registros reflejan un peculiar éxito de poblaciones suspensívoras, retrógradas y densas, de crinoideos y demuestran una extensión regional de poblaciones similares descriptas para el Eoceno superior de Antártida |
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